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The present study examines the high-temperature (500–800 °C) oxidation behavior of Fe-10Cr-(3,5) Al alloys and studies the effect of nanocrystalline structure and Al content on their resistance to oxidation. The nanocrystalline (NC) alloy powder was synthesized via planetary ball milling. The prepared NC alloy powder was consolidated using spark plasma sintering to form NC alloys. Subsequently, an annealing of the NC alloys was performed to transform them into microcrystalline (MC) alloys. It was observed that the NC alloys exhibit superior resistance to oxidation compared to their MC counterparts at high temperatures. The superior resistance to oxidation of the NC alloys is attributed to their considerably finer grain size, which enhances the diffusion of those elements to the metal–oxide interface that forms the protective oxide layer. Conversely, the coarser grain size in MC alloys limits the diffusion of the oxide-forming components. Furthermore, the Fe-10Cr-5Al alloy showed greater resistance to oxidation than the Fe-10Cr-3Al alloy. [ABSTRACT FROM AUTHOR]

Oxidation behavior of nanocrystalline and microcrystalline Fe–20Cr–3Al alloys was investigated at high temperatures (500–800 °C) in the present study. The nanocrystalline Fe–20Cr–3Al alloy was synthesized by high-energy ball milling followed by spark plasma sintering. The synthesized nanocrystalline Fe–20Cr–3Al alloy was annealed to prepare its microcrystalline counterparts. The nanocrystalline alloy exhibited superior oxidation resistance than its microcrystalline counterparts, which is explained by oxidation kinetics and nature of oxide formed on both the alloys. The presence of higher grain boundary area in the nanocrystalline alloy enhances the diffusivity on metal and as a result, a considerably more protective oxide layer formed on the nanocrystalline alloy. On the other hand, a considerably less protective oxide layer formed on the microcrystalline alloy due to limited diffusion of metal. Additionally, both the nanocrystalline and microcrystalline alloys exhibited superior oxidation resistance at 800 °C than that of 700 °C, which is contrary to common steels. [ABSTRACT FROM AUTHOR]